A Most Contagious Game (Rue Morgue Classic British Mysteries)

When a London businessman retires early and buys a Tudor mansion, he's quite surprised--and perhaps even a little pleased (retirement being pretty boring)--to find a skeleton hidden in a secret room in the house. The skeleton appears to be more than a 150 years old, so the local police leave it to the homeowner to solve the mystery. The police are much more interested in solving a local, modern murder. Somehow the two deaths are connected. First published in 1967, this is Aird's only non-Inspector Sloan mystery and a complete triumph.